Visual signs and symptoms of corticobasal degeneration

Corticobasal degeneration is a rare, progressive neurodegenerative disease and a member of the 'parkinsonian' group of disorders, which also includes Parkinson's disease, progressive supranuclear palsy, dementia with Lewy bodies and multiple system atrophy. The most common initial symptom is limb clumsiness, usually affecting one side of the body, with or without accompanying rigidity or tremor. Subsequently, the disease affects gait and there is a slow progression to influence ipsilateral arms and legs. Apraxia and dementia are the most common cortical signs. Corticobasal degeneration can be difficult to distinguish from other parkinsonian syndromes but if ocular signs and symptoms are present, they may aid clinical diagnosis. Typical ocular features include increased latency of saccadic eye movements ipsilateral to the side exhibiting apraxia, impaired smooth pursuit movements and visuo-spatial dysfunction, especially involving spatial rather than object-based tasks. Less typical features include reduction in saccadic velocity, vertical gaze palsy, visual hallucinations, sleep disturbance and an impaired electroretinogram. Aspects of primary vision such as visual acuity and colour vision are usually unaffected. Management of the condition to deal with problems of walking, movement, daily tasks and speech problems is an important aspect of the disease.

Threat-evoked anxiety disrupts spatial working memory performance:an attentional account

It is proposed that threat-evoked anxiety and spatial Working Memory (WM) rely on a common visuospatial attention mechanism. A prediction of this hypothesis is that spatial but not verbal WM should be disrupted in conditions of threat anxiety. Participants performed verbal and spatial n-back WM tasks in the presence or absence of threat of shock (shocks were not delivered). The presence of anxiety was assessed via heart rate recordings and self-report. Both measures clearly distinguished between WM blocks associated with threat of shock (Threat) and blocks, in which threat was absent (Safety). Performance on the spatial WM task was impaired in Threat relative to Safety. Furthermore, the more anxiety participants reported and the higher their heart rate in Threat compared to Safety, the more impaired was their spatial WM performance. This effect was not observed for verbal WM. The results indicate selective disruption of spatial WM performance by threat-evoked anxiety, interpreted in terms of more overlap in visuospatial attention between anxiety and spatial WM vs. anxiety and verbal WM.

The data type of spatial objects

A spatial object consists of data assigned to points in a space. Spatial objects, such as memory states and three dimensional graphical scenes, are diverse and ubiquitous in computing. We develop a general theory of spatial objects by modelling abstract data types of spatial objects as topological algebras of functions. One useful algebra is that of continuous functions, with operations derived from operations on space and data, and equipped with the compact-open topology. Terms are used as abstract syntax for defining spatial objects and conditional equational specifications are used for reasoning. We pose a completeness problem: Given a selection of operations on spatial objects, do the terms approximate all the spatial objects to arbitrary accuracy? We give some general methods for solving the problem and consider their application to spatial objects with real number attributes. © 2011 British Computer Society.